1. Field of Disclosure
This disclosure relates to a multi-band frame antenna, and more specifically, to a multi-band frame antenna to be used for multiple-input multiple-output (MIMO), Global System for Mobile Communications (GSM), General Packet Radio Service (GPRS), Enhanced Data-rates for Global Evolution (EDGE), Long Term Evolution (LTE) Time-Division Duplex (TDD), LTE Frequency-Division Duplex (FDD), Universal Mobile Telecommunications System (UMTS), High-Speed Packet Access (HSPA), HSPA+, Code Division Multiple Access (CDMA), Wideband CDMA (WCDMA), Time Division Synchronous Code Division Multiple Access (TD-SCDMA), or future frequency bands.
2. Description of the Related Art
The “background” description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventor, to the extent it is described in this background section, as well as aspects of the description which may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present invention.
As recognized by the present inventor, there is a need for a wideband antenna design with good antenna efficiency to cover Long Term Evolution (LTE), multiple-input/multiple-output (MIMO), and many other new frequency bands scheduled around the world. In a conventional wideband antenna, a plurality of ports (feeding points) of the antenna system usually correspond to a corresponding number of antenna components or elements. In a conventional two Port MIMO LTE antenna arrangement, top and bottom antennas may be a main and a sub/diversity antenna, respectively, or vice versa. The antennas are discrete antennas, optimized for performance in the frequency bands in which they were designed to operate.
The conventional wideband antenna designs do not generally meet the strict requirements in hand-head user mode (a carrier/customer specified requirement) and in real human hand mode (reality usage). These requirements have become critical, and in fact, have become the standard radiated antenna requirement set by various carriers (telecommunication companies) around the world. Hence, there is a need for a wideband antenna design with good antenna efficiency, good total radiated power (TRP), good total isotropic sensitivity (TIS) (especially in user mode, that is head-hand position), good antenna correlation, balanced antenna efficiency for MIMO system, and at the same time, good industrial metallic design with strong mechanical performance.
To make mobile devices look metallic, non-conductive vacuum metallization (NCVM) or artificial metal surface technology is conventionally used and widely implemented in the mobile device industry. A mobile device housing with a plastic frame painted with NCVM is very prone and vulnerable to color fading, cracks, and scratches.
The NCVM can cause serious antenna performance degradation if the NCVM process is not implemented properly, which has happened in many cases due to difficulties in NCVM machinery control, manufacturing process imperfections, and mishandling. Also, the appearance of NCVM does not give a metallic feeling, and looks cheap.
In order to effectively hold the display assembly of a mobile device, the narrow border of the display assembly requires a strong mechanical structure such as a ring metal frame. Conventional antennas for smartphones and other portable devices do not generally react well in the presence of a continuous ring of surrounding metal, as the metal negatively affects the performance of these antennas. Therefore, a continuous ring of metal around a periphery of a device is generally discouraged as it is believed to distort the propagation characteristics of the antenna and distort antenna patterns.
In one conventional device, a discontinuous series of metal strips are disposed around the electronic device to form different antenna segments. The strips are separated by a series of 4 slots, so that there is not a continuous current path around the periphery of the device. Each segment uses its own dedicated feed point (antenna feed, which is the delivery point between transmit/receive electronics and the antenna). This design uses multiple localized antennas with corresponding feed points. Each segment serves as one antenna, and requires at least one slot or two slots on the segment. Each segment acts as a capacitive-fed plate antenna, a loop antenna, or a monopole antenna. The difference between this design and a flexfilm/printing/stamping sheet metal antenna is that these antenna segments surround the outer area of the mobile device, while the flexfilm/printing/stamping sheet metal antenna is inside the device and invisible to the user.
As recognized by the present inventor, a problem with the antenna segments that surround the electronic device is that when a human's hands are placed on the smartphone, the human tissue serves as a circuit component that bridges the gap between segments and detunes the antenna, thus degrading performance. Moreover, these devices are sensitive to human contact due to the several slots being in direct contact with the human hand during the browsing and voice mode and creating a hotspot being around the affected slot.